I stumbled on this thread while looking to see if exactly this question (“use other mpd client with plexamp mpd”) had been asked/answered before.

MPD is short for “music player daemon”, a background server you can run on your computer that will allow multiple clients to connect to it and consume music. https://www.musicpd.org/ is the official project site.

Since Plex is obviously using some form of mpd, I too wonder: how complete of an mpd implementation is it? Are you using the actual official mpd source code with some special sauce to integrate with a Plex Media Server library? Could I modify the mpd configuration (I’m on MacOS) or throw another mpd client at it to get some of the features plexamp doesn’t yet have?